Ultrasound aided KMnO4-acid systems for bleaching linen fabric

Investigations were undertaken to optimize bleaching of linen fabrics using four systems, namely, KMnO4-oxalic acid, KMnO4-citric acid, ultrasound assisted KMnO4-oxalic acid and ultrasound assisted KMnO4-citric acid .The bleaching process involved two distinct steps where linen fabric was treated under different conditions with aqueous solutions of KMnO4 to yield MnO2-containing fabrics then the latter in a subsequent step was subjected to acid treatment under a variety of conditions. Optimization studies concerning the KMnO4 treatment refer to the following conditions.[KMnO4], 5 g/l at pH 4 and 90 °C for 20 min, whereas those of acid treatment were [oxalic acid], 10 g/l at 85 °C for 30 min. Similar conditions were found with citric acid except that its concentrations was 8 g/l. Introduction of ultrasound as an eco-friendly source of energy in the acid treatment step shortens the time from 30 min to 5 and 10 min in case of oxalic acid and citric acid respectively while decreasing the temperature from 85 °C to 60 °C for both acids.